The invention relates to an electronic sewing machine for electronically storing stitch control data which are sequentially read out with a timing pulse produced from a pulse generator operated in synchronism with rotation of an upper drive shaft of the sewing machine, to thereby control a stitch forming device. More particularly, the invention relates to a pattern varying device of the electronic sewing machine which is operated to control the transmission ratios between a data storing memory and the stitch forming device of the sewing machine as to vary the stitch width of a desired number of selected patterns with a predetermined variation rate for either progressively increasing or progressively reducing the stitch width of a series of such patterns.
According to the conventional electronic sewing machine, it is possible to vary or modify a pattern or a number of sequential patterns by manually adjusting a stitch width adjusting dial and a feed adjusting dial. However, such adjusting modes or values are determined during the production of the sewing machine at the factory, and therefore the variations or modifications of a pattern are limited. Moreover, when a number of sequential patterns is to be varied or modified with respect to a number of combined patterns, the machine operator is required to interrupt the running of the sewing machine each time one pattern is stitched so as to manually adjust the stitch width or feed amount for the next pattern. Such a manual operation is troublesome, and remarkably decreases the stitching efficiency.